This invention relates generally to video games and more particularly to an interactive game "film" which is stored on an optical disk (CDROM) and can be played on a microprocessor-based system.
A number of video games contain an animated virtual character, represented on a display screen, whose movements may be controlled by the actual player sitting before the display. The point of view of the virtual character in some instances is the same as that of the player, creating a "first person" relationship. In many simpler video games, the virtual character can be moved in any direction at any moment. In more realistic games, however, the character is constrained to follow a path from which he can vary only at certain opportunities, and even then the number of options may be limited. Greater realism, involving realistic backgrounds and correct rendering of moving objects at different depths from the viewer, places greater burdens on the computer processor, data storage device, host random access memory, and video display memory. Game designers have therefore had to compromise between the conflicting goals of extremely realistic rendering and providing the player with a sufficient number of choices to give the virtual character an entertaining degree of spontaneity.
In the following discussion, we use the term "player" to mean the person playing the game, and "protagonist" to mean the principal character or hero of the game.
In The Prisoner of Zelda, for example, the virtual protagonist, viewed always from a bird's eye point of view, can move at will in two dimensions through a palace of many rooms. The game is entertaining because of the many options the player has throughout the game; however, the rendering is cartoonish, and depth portrayal is poor.
Other games have been given better rendering, still short of realistic, at the expense of playing enjoyment. The so-called branching in some such games consists at points only of a correct choice and in incorrect one, the latter resulting in termination of the protagonist and thus the game. An example of this type of game is Dragon's Lair. The continuation of the animated story is dependent on the player's ability to make the right decision at key moments in the story. If, for example, the player fails to draw "his" sword when required, his protagonist is killed, and the game must be rerun. Since there is only one correct choice at each decision point, successful play of the game is always the same. Once such a game is played through, its appeal is greatly diminished.
Another problem with prior games which strive for representational realism is that there may be discontinuities ("seams") in the rendering, particularly when logical branching occurs. Such breaks disturb the player's illusion that he is actually participating in the action.
Part of the problem with prior games was that of storage access times. With tape-based systems, and to a lesser extent, disc-based systems, seek times from one scene to another were so great as to prevent seamless scene switching where there were logical branches. In MIT's Aspen Colorado Walking Tour, for example, one could explore the town of Aspen by selecting which way to turn at each corner. But at each decision point, motion halted while the next segment of film was cued up. There was no opportunity to buffer data to smooth the transition, since this was an analog system.
To overcome hardware limitations, some prior digital games used very large RAM buffers to store streams of data flowing from a storage device such as a CD-ROM.
Another approach was to interleave data on the storage medium. For example, where three alternative scenes were involved, every third data element would belong to one of the scenes, so that all three scenes were "present" at all times, and could be instantaneously switched between.